In general, there are chairs in a place where a number of people use such as a playground stand, an open theater, a park, etc.
Since the chairs which are installed in the above-described places are exposed in the outdoor environment, it is general to use chairs made of plastic materials having an excellent durability. These chairs are constituted by only a seat, or made of a seat and a back support which are integrally formed, respectively.
However, since the chairs are exposed in the outdoor environment, dust may be collected on the chairs, or the chairs may be wet due to the rain or snow, which causes it inconvenient to manage the chairs.
To solve the problem that the chairs are wet due to the rain or snow among the above-described problems, a seat is formed with an inclined structure to prevent rainwater from being collected, or is formed with the central portion positioned at a low position and having a drain hole to prevent rainwater from being collected. However, it is difficult to prevent the seat from being polluted due to foreign matters such as dust.
Thus, in order to prevent the seat from being polluted due to dust or rainwater, there has been introduced a chair having a structure that a back support hinged and connected with the rear end of a seat is used as a back support when the chair is used as a seat, and is used as a cover plate for the seat when the chair is not used as a seat.
However, in the case of a chair which employs a combined use of a back support as a cover plate for covering a seat of the chair in which the seat and the back support are hinged and connected with each other, a user should fold the back support to cover the seat with it. This causes difficulties of management of chairs.
In order to solve the problems, the same applicant as that of the present invention developed and filed Korean Patent Application No. 2001-16600 on 29 Mar. 2001 (Korean Laid-open Patent Publication No. 2002-76617 published on 11 Oct. 2002), entitled “A chair with a combination back support and cover plate.” Here, a twist spring is installed in a hinge pin combined between a back support and a seat. Accordingly, in the case that a user stands up from a riding state on the seat, the back support is automatically folded on the seat.
However, since the back support is always elastically supported on the upper surface of the seat by the twist spring, a user who wishes to sit on the seat should raise up the back support with one hand until he or she sits thereon.